Improvement in electric fuses



T. VARNEY.

Electric-Fuses.

Patented March1o,1874.

THOMAS VARNEY, or sAN FRANCISCO, CALIFORNIA.

IMPRQVENIENT iN ELECTRIC FUSES.

Specification forming part of Letters Patent No. 148,338, dated March 10, 1874 application filed November 15, 1873.

To all whom it may concern:

Be it known that I, THOMAS VARNEY, of the city and county of San Francisco and State of California, have invented an Improved Electrical Exploder, -of which the following is a specification:

The object of my invention is to prepare, in a cheap and simple manner, the percussion or fulminating cap, commonly used to explode dynamite and other like substances, for being itself exploded with ease and certainty byelectricity, and at the same time to have the cap and its attachments when thus prepared (then called an electrical exploder) small, convenient for use, and secure against being injured by violence, dampness, time, or temperature, and also secure against accidental expiosion.

The accompanying longitudinal central section view of my explodcr enlarged forms a part of this specification.

The kind of wire best adapted to my purpose, so far as I am now infin-med, is that known as gutta-percha wire, Xo.- 14 outside and No. 24 inside-that is, the copper wire is No. 24, and covercd"\\'ith so much guttapercha as to make it No. 1i outside of all. This size ot wire and covering proves to be satisfactory in the distance between the copper extremities wit-hin the cap, in the room it occupies, in the insulation it a-iords, in the current it is able to carry, in strength, in its security against injury, in tamping, and in all other 'partielllars.

The electro-sensitive powder made use of by me is made as follows: Ten parts of subphosphide of copper, forty-five parts of subsulphide of copper, and fifteen parts of chlorate ot potash. Meisten them well with alcohol, and pulverize, and thoroughly mix in a morter. Carefully dry, and keep in close vessels.

The exploder is constructed as follows: The wire is rst cut into lengths somewhat' greater than the depth of bore-hole iu which they are to be used. The cutting should be done with nippers having sharp edges that meet, so as to leave the ends of the wires .as regular and little disturbed as possible. As much of the sensitive powder as will lie on the point of a pen-knife, or just suificient to cover the' face of the fuhninate within the cap, is put into the it to adhere, then press the wires togetherA while they cool. Thisinsures the yproper distance between the wires. 'lhe ends of the wlre'thus stuck together are now inserted into the eap,`and into contact with the sensitive powder, and the vacant space about them in the cap ille-d with molten sulphur. perat-ure should not be allowed to rise but very slightly above thevinelting-point, or the sulphur will become too thick to till in wells Referring to the drawing, A i's the shell of the cap; B, the fulminate; C, the copperwires; D, the gutta-percha; E,I the electro-sensitive powder, and F the sulphur.

It will be observed that the size of the exploder proper 'does not exceedthat of the cap. The junction of the several parts is made within the cap. "his is very important. A large plug of wood, paper, or other compressible material diminishes, the eicctiveness ot' the blast.

The ease and certainty with which the metallic ends of the wires are placed at a proper and uniform distance apart and in contact with the sensitive powder is' apparent. The sulphur holds the wires so firmly that it requires great force to displace them, and its s olidit-y and hardness protect the fulminates from percussions, a s-well as from all exterior influences. lhus we have all the essential qualities of a good exploder-compactness, solidity, `Jafety, durability, uniformity, and eheapness.

' Having thus described my invention, what I claim as new, and desire to secure by Letters Patent. is

An electric fuse composed of a single shell containing the requisite fuhninate or detonating powder, the'electro-sensitive powder, and the ends of the conducting-wires, all in proper contact, and secured therein by sulphur,'or its equivalent, substantially ink the manner and for the purpose set forth.

THOMAS VARNEY.

Witnesses: 1r-

Jr Cuirs.l M. BURNS.

f *renfe Errea The tenil 

